1. Field of the Invention
The present invention relates to design support methods and programs and, in particular, to a design support program and a design support method which can be advantageously used for achieving optimal design of a conveying path for a sheet-like material.
2. Description of the Related Art
In designing a conveying path, it is desirable that the function of a designed object is examined under various conditions before the actual fabrication of a product. Such examination can reduce the number of processes required to manufacture and test a prototype, and can reduce the development period and cost. As a technique for simulating the behavior of a sheet in a conveying path, a finite element method for a recording medium is used.
Specifically, Japanese Patent Laid-Open No. H11-195052 and Japanese Patent Laid-Open No. H11-116133 disclose design support programs. In these programs, a conveying resistance and a contact angle between a recording medium and guides or rollers for the recording medium are evaluated by expressing the recording medium as finite elements. Then, contact conditions between the recording medium and the guides or rollers in the conveying path are determined by numerically solving a motion equation.
The motion of a recording medium is solved by formulating a motion equation of the recording medium discretely represented by finite elements or mass-spring systems. Then, an analysis target time period is divided into time steps each having a finite length, and the motion of the recording medium is solved by numerical time integration that sequentially calculates unknown accelerations, velocities, and displacements in the respective time steps starting from time 0. This technique is well known as Newmark β method, Wilson θ method, Euler's method, Kutta-merson method, and the like (see, for example, Katsuhito Sudoh, “Modeling a String from Observing the Real Object” Proc. of Int. Conf. on Virtual Systems and Multimedia (VSMM2000), pp. 544-553, (2000)).
For example, Japanese Patent Laid-Open No. 2004-258774 discloses a technique for performing such a simulation. In this technique, a conveying path is rendered on a two-dimensional plane by line segments including a strait line, an arc, and a spline curve so that the conveying path is designed.
In another technique, shape data created by a CAD (computer-aided design) system is converted into simulation data. In this case, application software which performs preprocessing for creating a simulation model is generally used. Such application software allows a user to create a contact definition and a simulation condition definition including input of physical property values.
Further, with a view to reducing the processing load for a simulation, for example, Japanese Patent Laid-Open No. 2000-331194 discloses a model creating technique in which holes or fillets unnecessary for simulation are omitted.
In such design support programs described above, a recording medium is divided into a finite number of elements or masses, and a reacting force between the recording medium and conveying guides is generated by performing contact calculation between one element or one mass and one line segment constituting the conveying path. Thus, the program reproduces complicated behaviors of the recording medium in the conveying path.
The contact calculation is performed for each time step of numerical time integration. Thus, the calculation load for the numerical time integration disadvantageously increases with increasing number of elements or mass points of a recording medium and increasing number of line segments forming a conveying path, resulting in prolonged calculation time.
When a two-dimensional model having a principal cross-section projected from a three-dimensional CAD drawing is created, the model includes a number of unnecessary parts that are irrelevant to sheet conveyance. In such a case, the number of line segments exceeds five thousand in the case of a typical copying machine. Such a model requires ten hours or more for behavior calculation and is not able to meet users' needs as a design support tool. Therefore, it is desirable to omit parts which do not come into contact with a recording medium from the calculation model.
However, in order to create a model for a recording medium conveying simulation on the basis of a design drawing based on a three-dimensional CAD, it is necessary for a user to manually determine contact parts between a recording medium and a conveying path and erase parts other than the contact parts. This operation takes the user considerable labor especially when a drawing to be processed is large, and lacks accuracy. To address this, Japanese Patent Laid-Open No. 2003-337836, for example, discloses a method in which a FEM (finite element method) model based on a shape characteristic is automatically created by a device on the basis of creation processes stored in a database.